Recent features in EBSD, including new trapezoidal correction for multi-mapping

EBSD (electron backscatter diffraction) of geological samples can be a challenge due to the complex crystal structures of minerals and commonly 5 or more different minerals in the samples. This poses a big challenge as the EBSP (electron backscatter diffraction patterns) of the minerals like feldspar and quartz commonly are much noisier than metallurgical materials that have simpler structures. Therefore, the indexing of geological samples can commonly be quite difficult and to correct for this in the online procedure means that the data acquisition needs to be redone on the SEM. This is a costly procedure, also because the indexing can take longer than the pattern acquisition itself. We, therefore, suggest that offline techniques are better suited for geological materials because the patterns can be re-indexed using different settings and further can be processed using different software both for indexing and pattern improvement. EBSD commonly have geometric scan distortion which increases with decreasing magnification. This problem is solved by acquiring using a geometric online scan correction during data collection in the NORDIF software using calibration grid. This overcomes stitching problems and additionally removes hidden problems such as geometrically distorted grain boundary segments and grain shape distortions.